1. Field of the Invention
The present invention relates generally to wireless communications and more particularly to a system and method for de-interleaving data in a wireless receiver.
2. Discussion of the Related Art
The Third Generation Partnership Project (3GPP) represents the joint effort of various standards setting bodies to produce globally applicable technical specifications and technical reports for the Universal Mobile Telecommunications System (UMTS). The UMTS is based on evolved Global System for Mobile Communications (GSM) core networks and the radio access technologies that they support (i.e., Universal Terrestrial Radio Access Network (UTRAN) including both Frequency Division Duplex (FDD) and Time Division Duplex (TDD) modes).
The 3GPP UTRAN FDD transmitter chain includes two interleavers. The first interleaves data to be transmitted into different radio frames, and the second interleaves the data inside each radio frame. The transmitted radio frames must then be de-interleaved at the receiver. Conventional receiver designs include two de-interleavers that mirror the operations of the two interleavers in the transmitter. Each de-interleaver according to conventional designs has an associated memory buffer. The memory buffer associated with the second de-interleaver is double buffered so that the data received from the air in the current radio frame can be written into memory (a first buffer) while the rest of the receiver chain processes data from the previous radio frame (a second buffer). The memory buffer associated with the first de-interleaver does not have to be double buffered because the data can be processed asynchronously (as long as the data is processed in one radio frame).
A read/write unit is used to read from and write to the memory buffers. The read/write unit includes, for example, programmable logic for generating memory buffer addresses. According to conventional designs, a separate read/write unit is associated with each memory buffer. These read/write units require an amount of chip real estate and power that can be significant in terms of the receiver design. This is particularly true where chip real estate and power usage are at a premium, such as in the design of wireless handsets. Furthermore, moving the receiver data between the two de-interleaver memory buffers requires two write operations and two read operations for every bit of received data. Performing each of these operations requires power, which again can be particularly significant where conserving power usage is important.
What is needed is an improved system and method for de-interleaving data in a wireless receiver, where chip real estate and power usage are reduced.